Numerical simulation study on the effect of gas extraction in one face and four lanes on the spontaneous combustion of coal remains in the mining area

In order to study the “three zones” of spontaneous combustion in gob under different gas treatment conditions of high gas prone to spontaneous combustion and the change law of temperature field distribution, combined with the actual conditions of a high gas prone to spontaneous combustion working surface, a physical model of spontaneous ignition in goaf with “one face and four lanes” was constructed. The oxidation oxygen consumption and heat release parameters of coal samples obtained from temperature programmed experiment were applied to numerical simulation. The influence of different air supply, low and high pumping flow on the “three zones” of spontaneous combustion and temperature field distribution in goaf was studied. The variation of parameters such as maximum width of oxidation zone, area of oxidation zone and maximum temperature point of goaf with air supply, low and high pumping flow was quantitatively analyzed. The results show that in the range of simulation test, increasing air supply, low pumping flow and high pumping flow will cause the increase of air leakage in goaf, which is not conducive to the prevention and control of spontaneous combustion of coal left in goaf. The maximum temperature point does not change significantly (only within the range of 1K), and the influence of the change of high pumping flow rate on the width and area of the oxidation zone and the maximum temperature of the goaf is greater than that of the air supply volume and low pumping flow rate. The maximum width of oxidation zone increases with the increase of air supply, and the maximum temperature of goaf and the area of oxidation zone decrease with the increase of air supply. When the air supply increases from 1600 m³/min to 1900 m³/min, the maximum width of oxidation zone increases by 2 m (74−76 m), and the maximum temperature decreases by 0.1 K (315.38−315.28 K). The oxidation zone area decreased by 180.08 m² (8 669.49−8 489.41 m²). The maximum width of oxidation zone increases with the increase of low extraction flow rate, the maximum temperature of goaf and the area of oxidation zone increase with the increase of extraction flow rate. When the low extraction flow rate increases from 200 m³/min to 300 m³/min, the maximum width of oxidation zone increases by 2 m (75−77 m). The maximum temperature increased by 0.152 K (315.34−315.492 K), and the oxidation zone area expanded by 51.56 m² (8 553.79−8 605.35 m²). When the high pumping rate increased from 80 m³/min to 240 m³/min, the maximum width of the oxidation zone remained at about 75 m, and the maximum temperature increased by 0.76 K (315.13−315.89 K).